{"id":"F2006B07397","name":"AD/TFE 731/14 - First Stage L.P. Turbine Disc","slug":"ad-tfe-731-14-first-stage-l-p-turbine-disc","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":49598,"registerId":"commonwealth-F2006B07397-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/TFE 731/14 - First Stage L.P. Turbine Disc","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 106 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nAlliedSignal (Garrett/AiResearch) Turbine Engines \\- TFE731 Series\n\nAD/TFE731/14 First Stage L.P. Turbine Disc 9/88 TX\n\nApplicability: TFE 731-5 series engine with suspect first stage L.P. turbine disc whose serial numbers are identified in the Requirement document.\n\nRequirement: Remove from service affected first stage L.P. turbine discs in accordance with\n\nG.T.E.C. Alert SB TFE 731-A72-3371.\n\nCompliance: For discs with less than 750 operating cycles: Prior to exceeding 750 operating cycles.\n\nFor discs with more than 750 operating cycles: Replace within 25 operating cycles after 27 June 1988.\n\nBackground: This Directive is issued to reflect GTEC Alert SB TFE 731-A72-3371 which advises the recent in-flight shutdown caused by separation of 2 adjacent firtree posts and release of three turbine blades. Engineering investigation determined that discs had been manufactured from a suspect forging lot.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific manufacturing defect in a specific engine component. It has not expanded beyond its original purpose of mandating replacement of suspect turbine discs."},"complexity_factors":["Single, specific mechanical component targeted (first stage L.P. turbine disc)","Simple conditional logic based on operating cycle count (two clear categories: <750 vs >750 cycles)","Heavy reliance on external technical document (G.T.E.C. Alert SB) for serial numbers and detailed procedures","No nested exceptions or complex cross-referencing within the directive itself","Clear, fixed compliance dates and cycle counts","Limited to one engine series (TFE 731-5)"],"plain_english_summary":"This is an **Airworthiness Directive** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) that requires specific maintenance action on aircraft engines.\n\n**What it does:**\nOrders the removal from service of certain **first stage low-pressure (L.P.) turbine discs** found in **TFE 731-5 series engines** made by AlliedSignal (formerly Garrett/AiResearch).\n\n**Who it affects:**\n- Aircraft operators using TFE 731-5 series engines\n- Specifically those engines with turbine discs from a particular batch of faulty forgings (the exact serial numbers are listed in a separate technical document referenced here)\n\n**Why it matters:**\nA manufacturing defect in these discs caused an **in-flight engine shutdown** when parts of the turbine disc broke off during flight, releasing turbine blades. This could lead to catastrophic engine failure. The directive prevents this by forcing replacement of the faulty discs before they reach a dangerous number of flight cycles.\n\n**The deadline depends on usage:**\n- **Low-use discs** (under 750 flight cycles): Must be replaced before hitting 750 cycles\n- **High-use discs** (over 750 cycles): Must be replaced within 25 cycles after 27 June 1988\n\n**Key technical reference:**\nOperators must follow the specific procedure in **G.T.E.C. Alert Service Bulletin TFE 731-A72-3371** to complete the replacement."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The directive implements and reflects the G.T.E.C. Alert SB by requiring removal/replacement of discs from a identified suspect forging lot; it confines action to the discs whose serial numbers are identified in the Requirement document and does not expand scope beyond that identification (Applicability; Background)."},"complexity_factors":["Limited applicability to specific serial-numbered discs (Applicability).","Direct reference to an external service bulletin (G.T.E.C. Alert SB TFE 731-A72-3371) for technical compliance steps (Requirement).","Two discrete compliance timelines based on operating-cycle thresholds (<750 cycles and >750 cycles) and a fixed calendar date for the >750-cycle category (Compliance).","Necessitates verification of serial numbers and operating-cycle counts by operators (Applicability; Compliance)."],"plain_english_summary":"This AD mandates removal and replacement of certain first-stage low-pressure turbine discs on AlliedSignal TFE731-5 engines whose serial numbers are listed in the directive, citing an in‑flight shutdown linked to a suspect forging lot. It affects operators/owners and maintenance organisations, and requires compliance with the referenced G.T.E.C. Alert Service Bulletin on the timelines for removal or replacement."}},"importantCases":[],"_links":{"self":"/api/acts/ad-tfe-731-14-first-stage-l-p-turbine-disc","history":"/api/acts/ad-tfe-731-14-first-stage-l-p-turbine-disc/history","analysis":"/api/acts/ad-tfe-731-14-first-stage-l-p-turbine-disc/analysis","conflicts":"/api/acts/ad-tfe-731-14-first-stage-l-p-turbine-disc/conflicts","importantCases":"/api/acts/ad-tfe-731-14-first-stage-l-p-turbine-disc/important-cases","documents":"/api/acts/ad-tfe-731-14-first-stage-l-p-turbine-disc/documents"}}